Direct beam solar light system

ABSTRACT

A direct beam solar lighting system for collecting and distributing sunlight into a room. The system includes a rotatable solar collector head to receive sunlight and to reflect the sunlight downward into a transition tube having a reflective interior surface. The light-concentrating transition tube reflects sunlight into a reflective light tube which directs the reflected sunlight through a plenum space into the room. The system includes a drive mechanism for rotating the rotatable solar collector, and a light fixture at end of the light tube to disburse said reflected sunlight onto a ceiling and a wall in the room. In an embodiment the system includes one or more homogenizing reflectors within the solar collector for collecting the sunlight and directing the sunlight more uniformly over the aperture of the transition tube. In an alternative embodiment, the solar collector includes a rotatable tiltable mirror for providing two-axis tracking.

This application is a divisional application of U.S. application Ser.No. 11/501,523 filed on Aug. 9, 2006, now U.S. Pat. No. 7,639,423allowed, which claims the benefit of priority to, U.S. ProvisionalApplication No. 60/706,955 filed on Aug. 10, 2005.

FIELD OF THE INVENTION

This invention relates to solar interior lighting and, in particular, tomethods, systems, apparatus and devices for implementing a direct beamsolar lighting system for collecting, transmitting, and distributingsunlight into an indoor room with optional supplemental lighting.

BACKGROUND AND PRIOR ART

Competing technology can be divided into two categories. The firstcategory includes conventional toplighting with rectangular roofskylights, clerestories, roof monitors, roof windows, and tubularskylights, the latter known generically as tubular daylighting devices(TDDs). Some problems exhibited by most of these include:

1. Glare potential, from direct beam sunlight entering the space in sucha way that people can see this very bright light directly (andindirectly by reflection from surfaces in the room).

2. Solar overheating, resulting from large aperture areas not moderatedby heat shading or reflecting surfaces or shades.

3. Wintertime heat loss by conduction, convection, and radiation of roomheat upward through the skylight to the outdoors, especially troublesomeon cold winter nights.

4. A common need for custom architectural work, to adjust the buildingdesign to accommodate the daylighting system without excessive glare oroverheating, this adding to the cost and complexity of the installation.

5. Spatially non uniform illumination over the space.

6. Temporally non uniform illumination over the course of the day, asthe sun rises, moves through the sky, and sets.

One or Two-Axis Tracking

The second category of potentially competing technology, based on one ortwo-axis tracking designs, utilizes concentrating solar collectors ofthe “dish” reflector or Fresnel lens type, coupled with sophisticatedoptical systems to capture the concentrated solar flux and put it intolight pipes for distribution to building spaces. Some of thedistribution systems utilize solid or liquid light pipe media, such asfiber optics. Some of the problems exhibited by prior art daylightingsystems include:

1. High expense for the design and manufacture of the high-qualityoptical components, such as primary mirrors, lenses, or specialnon-imaging concentrators, and relay mirrors and lenses.

2. High expense for the complex mechanisms required to track the sun viathe primary mirror in both azimuth and altitude.

3. High expense to design and fabricate the building to accommodatethese complex optical systems.

4. Propensity for tracking mechanisms to fail when exposed to the sunand weather.

5. Light losses, both in flux transmitted and color distortions,associated with absorption of light flux as it travels through solid orliquid media.

6. Tracking mechanisms often require high accuracy and must becalibrated to and maintain tight tolerances

The primary problem with TDDs and horizontal rectangular-aperture roofskylights is that as the sun's altitude angle (angular distance abovethe horizon) decreases, the effective size of the device's entranceaperture decreases as well, so that less flux is captured by the device(while the potential heat loss remains high, especially for largeaperture skylights). Furthermore, as the solar altitude decreases, theangle of incidence on the wall of the reflective light tube (or theskylight well or shaft) also increases, thereby increasing both fluxabsorption per reflection and the number of reflections for a ray ofsunlight to propagate down the tube to the space below. The result is asubstantial decline in skylight illumination performance with solaraltitude angle.

In order to capture enough diffuse sky light flux at low sun angle(mornings and afternoons), both TDD and conventional skylight apertureshave to be increased. With these enlargements also come increases inheat flux into and out of the building through the skylight by themechanisms of radiation, conduction, and convection.

Sidelighting from windows in walls is not included in the abovecompeting options because it is not available for the core spaces ofbuildings, far removed from an exterior wall, the subject of thisapplication is also intended to provide daylight illumination to areasadjacent to the window when for various reasons the window illuminationis inadequate, and because this invention is also intended to providedaylight illumination to both spaces distant from a window wall andwindowless building spaces even when they are adjacent to an exteriorwall.

The prior art includes conventional rectangular- and round-aperture roofskylights, including those with planar, domed, and pyramidal glazingmade of glass or transparent plastic, and tubular daylighting devices ofall kinds. Specific patents more closely allied with the currentapplication are listed below.

U.S. Pat. No. 5,493,824 issued to Lee Webster on Feb. 27, 1996 describesa system whereby a glazed aperture faces the sun and is tracked inazimuth. It also contains reflective vanes behind the glazing whichredirect incident direct beam sunlight downward into the room below. Thevanes also are adjusted to optimize performance as the sun moves up anddown relative to the device. The device described includes a housingwith an opening for receiving sunlight. The opening is covered with anultraviolet-deflecting lens and the housing contains reflectors whichdirect sunlight through a conduit to a diffuser. The housing rests uponand is rotatable with respect to an annular base. A horizontal sensorarrangement controls rotational movement of the housing with respect tothe base to maintain optimum horizontal alignment of the reflectors withrespect to the sun. A vertical sensor arrangement causes verticalangular movement of the reflectors to maintain optimum verticalalignment of the reflectors with respect to the sun. The light conduitcontains an infrared-deflecting lens to filter out infrared radiation. Adead air space placed in the light conduit prevents heat transfer aslight is transmitted along the conduit.

U.S. Patent Publication No 2004/0118447 by Muhs is similar to U.S. Pat.No. 6,128,135 issued to Stiles et al. on Oct. 3, 2000 because theprinciples of operation and much of the optics are quite similar. Thedifference is that Muhs lacks a tertiary reflector, which in the Kinneycase is planar. Instead, the Muhs patent sends the light from thesecondary mirror to a flexible fiber optic bundle, an expensive optionwith potential optical problems. There could also be differences in theshapes of the primary and secondary mirrors between the two patents. TheKinney primary mirror is concave parabolic and the secondary is convexparabolic.

U.S. Patent Publication No. 2004/0050380 by Hiroshi Abe shows anelectronic diagram that has reflective vanes which track in azimuth andthat the vanes are tilted from the vertical by varying amounts. Thepurposes of the vanes are different in the two designs. In the Abepatent, these vanes are the primary reflecting means to redirectsunlight downward into the room below. The second two-axis trackingsystem has no multiple tracking reflecting vanes.

U.S. Pat. No. 6,691,701 issued to Roth on Feb. 17, 2004 is nearlyduplicate of the '139 tracking patent, in having a primary mirror with ahole in it, a secondary reflector, and a tracking planar tertiaryreflector sending a beam of concentrated sunlight vertically downwardinto a light pipe.

U.S. Pat. No. 6,557,804 issued to Carroll May 6, 2003 is intended forspace propulsion, not for illumination and shares no similarity with thecurrent application, except possibly through the gear and motor rotatingmechanism.

U.S. Pat. No. 6,299,317 issued to Gorthala on Oct. 9, 2001 is a cleverdesign involving components that have been known generically for sometime, but has limitations mainly due to the large spread of the raysemerging from the secondary concentrator into the optical fiber, meaningthat many of the rays from the concentrator will be incident at largeangles on the fiber entrance aperture and will undergo many reflectionsand increased path lengths through the optical fiber, causingsubstantial losses along the way. Heating of the optical fiber throughabsorption when the sky is clear and with high concentration ratios is aproblem noted by other experimenters attempting to use solid light pipesin similar applications.

U.S. Pat. No. 5,907,648 issued to Miller on May 29, 1999 describes abeam fiber optic spotlight luminaire and U.S. Pat. No. 4,720,170 issuedto Learn discloses tracking primary and secondary mirrors, like the Muhspatent, sending concentrated beam sunlight into a fiber optic or otherflexible light pipe and suffers from the problems of such mentioned inthe description the 2004/0118447 publication. The patent's FIG. 2 offersa methodology for ameliorating the problem by passing the capturedconcentrated beam sunlight through a column of clean water, therebystripping off much of the infrared portion of the solar spectrum, asdescribed in McCluney, Ross, “Color-rendering of daylight fromwater-filled light pipes,” Solar Energy Materials, Vol. 21, 2-3 Dec.1990, pp. 191-206. FIG. 3 offers a methodology similar to the Stilespatent for directing the concentrated daylighting into a light pipe, butthis method requires a flexible light piping system to accommodatedeclination changes and places the planar reflector in front of theprimary mirror. This is an equatorial design requiring seasonaladjustment of the declination but which tracks around an axis throughthe light pipe on a daily basis. This patent offers the uniquecharacteristic of claiming a military use of solar energy. A means ofswitching between solar and electric lighting is claimed butinsufficiently described.

U.S. Pat. No. 4,429,952 issued to Dominguez is the one knowncommercially as the “Sol-Luminaire” skylight, a skylight with a trackingplanar mirror above it. This is a closed loop design, it obtainsfeedback from the position of the sun and corrects itself based on thisfeedback. This method can be fooled by passing clouds.

U.S. Pat. No. 4,389,085 issued to Mori on Jun. 21, 1983 is a daylightingsystem that was promoted for a while a decade or two ago. It suggests avariety of means for collecting sunlight and distributing it to interiorspaces. All are relatively high-tech in nature and generally areexpected to be expensive. No control system is claimed. Theunconventional Fresnel-lens-like drawings are clever and interesting,but probably more artistic in use than practical.

U.S. Pat. No. 4,246,477 issued to Latter on Jan. 20, 1981 is anequatorial tracking Fresnel lens plus reflectors and piping system withlenses for refocusing the solar beam for long-distance piping anddistribution into buildings. The Fresnel lens as shown is too small todeliver useful illumination to all but a tiny area of a building.Scaling it up to large enough size to be useful might be possible, butexpensive. The extensive piping system in particular, with associatedhigh-quality optical components, should prove very expensive andeconomically prohibitive.

U.S. Pat. No. 4,086,485 issued to Kaplow in 1978 suggests the use of anarray of apparently small Cassegrain telescopic systems with primary andsecondary mirrors, meaning that the whole system requires tracking,apparently for focusing solar radiation onto small photovoltaic sensorsfor the generation of electricity. No means for illuminationdistribution are shown in the drawings and the means of tracking is notvery clear. This patent has a closed loop system for tracking.

SUMMARY OF THE INVENTION

A primary objective of the invention is to provide new methods, systems,apparatus and devices to provide daylight illumination to buildingspaces with or without windows.

A secondary objective of the invention is to provide new methods,systems, apparatus and devices to provide an optical design of theaperture, reflecting mirror, and light shaft to accommodate solaraltitude variations without the need for additional tracking, whileincreasing throughput at low sun angles and attenuating it at highvalues, to provide more constant illumination throughout the day.

A third objective of the invention is to provide a new method, system,apparatus and device making up a retroreflector to direct sunlightexiting the lower portions of the system onto a light-colored (diffuselyreflecting) ceiling from which light is diffused into the space below,resulting in low-glare, and well-distributed natural light falling onwork surfaces.

A fourth objective of the invention is to provide new methods, systems,apparatus and devices to improve the capture of flux from the sun whenthe sun is near the horizon.

A fifth objective of the present invention is to provide new methods,systems, apparatus and devices that requires little alteration ofbuilding design and reduce the space needed between the roof and ceilingfor installation.

A sixth objective of the invention is to provide new methods, systems,apparatus and devices for direct beam solar lighting systems using anoptical system that provides near maximum delivery of illumination tothe workspace with an acceptably large azimuth tolerance in order toreduce fluctuations of the delivered illumination during operation dueto intermittent tracking actuation, thereby allowing duty-cycledoperation rather than continuous tracking, and also expandingorientation error limits.

A seventh objective of the present invention is to provide apparatus,methods, systems and devices for a single-axis tracking mechanism thatis very simple, inexpensive, and can be made to be very reliable anddurable. In addition, the system of the current application uses aretroreflector to direct sunlight exiting the lower portions of thesystem onto a light-colored (diffusely reflecting) ceiling from whichlight is diffused into the space below. The result is low-glare,well-distributed natural light falling on the work surfaces below.

The present invention seeks to overcome problems through the use of anaperture that faces more toward the horizon, coupled with mirrors thatreflect near-horizon sunlight down a light shaft into the room belowwhere it may strike a retroreflector, while attenuating radiation fromthe sun when it is higher in the sky, thereby balancing the problemsconventional horizontal skylights and tubular daylighting devices havewith low flux throughput at low sun angles and excessively high flux athigh sun angles. In order to maintain good flux-capturing abilitythroughout the day, the entire head, or sun-capturing component, of theprimary embodiment of this invention is made to rotate around a verticalaxis, tracking the sun's movement in azimuth only. Thus, relative to thesun-capturing component, the sun only moves up and down in the skythroughout the day.

The optical design of the aperture, reflecting mirrors, and light shaftare made to accommodate these solar altitude variations without the needfor additional tracking, increasing throughput at low sun angles andattenuating it at high angles to provide more constant illuminationthroughout the day. The sun's apparent motion up and down in the skyrelative to the system (elevation) is accommodated by the optical designof the system, which is intended to accentuate the capture anddistribution of sunlight when the sun is low in the sky, near to thehorizon. As the sun climbs higher in the sky relative to theazimuth-rotating sun harvesting head, its illuminance increases due toincreasing atmospheric transmittance (higher sun rays pass through lessatmosphere than do lower ones). The sun harvesting head presents adecreasing projected aperture area as the sun rises, thereby attenuatingthe sun's flux with increasing solar altitude angle, producing roomillumination that is more constant in time over the course of a day.

In an embodiment, the reflective elements that move to track the sun areencapsulated within a fixed, transparent enclosure. The difference isthat it allows for the moveable elements to be very light weight sincethey are not exposed to the forces of external weather. The benefits arethat the overall design is smaller and lighter in weight, it requiresvery little power to operate, the mechanism will not get jammed due tothe accumulation of ice or snow, and a sliding weather seal is notrequired. The moving elements are supported on a vertical axis with abearing (or bushing) at top and bottom. The lower bearing is directly inthe path of the solar flux that is being routed from the moveablereflecting elements to the light pipe and is supported by either atransparent surface or a plurality of narrow spokes in order to minimizelight losses.

For the third embodiment, reflective rectangular vanes 5 shown in FIGS.8 and 9 are added to the sun-harvesting head, as a novel means forsending light from the head more uniformly over the redirectingreflector 9 and 10 in the drawings. The result is more uniformdistribution of light around the room. The outer diameter of lowerreflecting ring 10 is made large enough so that rays emerging from thelight pipe 8 cannot reach human occupants of the room directly, therebyreducing glare.

In the fourth embodiment, additional reflecting rings 11 shown in FIGS.10 and 11 are added as alternate glare reduction elements. Their purposeis to allow lower reflecting ring 10 to have a smaller diameter whilestill preventing rays emerging from light pipe 8 from reaching humanoccupants of the room directly.

Further objects and advantages of this invention will be apparent fromthe following detailed description of preferred embodiments which areillustrated schematically in the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a basic configuration of the solar lighting system of thepresent invention.

FIG. 2 is a perspective view of the solar lighting system of the presentinvention.

FIG. 3 is a side view of the top section of the solar collection deviceincluding the rotation mechanism.

FIG. 4 shows a 3-dimensional perspective view of the solar collectiondevice.

FIG. 5 is a side view of the top section of the solar collection deviceencapsulated within a fixed, non-rotating transparent housing and lowerportion of the fixed housing.

FIG. 6 is a perspective view of the light pipe and reflecting rings forinstallation of the solar light fixture in a ceiling.

FIG. 7 is a side view showing one embodiment of how an electricluminaire can be incorporated with the solar lighting system of thepresent invention.

FIG. 8 shows the solar lighting system including reflective vanes in thesolar collection assembly.

FIG. 9 is a side-view of the solar collection head, illustrating theplacement the beam-homogenizing reflective vanes.

FIG. 10 shows the addition of reflecting rings as a glare preventionstrategy.

FIG. 11 is a view showing additional reflecting rings and theinstallation of the light pipe in a ceiling of a building.

FIG. 12 is a side view showing the light pipe, the reflective rings, andhow a transparent protective sleeve can be placed around the rings in aceiling of a building.

FIG. 13 shows the solar lighting system incorporating crossed reflectivebeam homogenizing vanes.

FIG. 14 is a side view of the solar lighting system of FIG. 13.

FIG. 15 shows the solar lighting system incorporating curved or roundedbeam homogenizing reflective vanes.

FIG. 16 shows a rectangular variation of the beam homogenizer shown inFIG. 15.

FIG. 17 is a side view showing a curved reflective mirror 26 in thesolar collection assembly.

FIG. 18 shows installation of the solar lighting system with a tubularskylight reflective cylinder.

FIG. 19 is a side view showing installation of the solar lighting systemwith a tubular skylight reflective cylinder on a roof of a building,providing more mounting details.

FIG. 20 shows installation of the transparent encapsulating housingversion of the solar lighting system of the present invention inconjunction with a tubular skylight reflective cylinder on a roof of abuilding.

FIG. 21 is a side view showing installation of the encapsulated versionof the solar lighting system in conjunction with a tubular skylightreflective cylinder on a roof of a building.

FIG. 22 shows a variation on the solar collection head with tworectangular glazings and an interior reflective solar altitude trackingmirror in the solar collection assembly.

FIG. 23 is a side view of FIG. 22 showing movement of the interiorreflective tracking mirror.

FIG. 24 is a side view of the invention incorporating an equatorialtracking mount.

FIG. 25 is a side view of the equatorial design shown in FIG. 24.

FIG. 26 is a side view of a version the design shown in FIG. 24 whereinthe solar collection head rotates and tracks about an axis parallel tothe Earth's axis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining the disclosed embodiments of the present invention indetail, it is to be understood that the invention is not limited in itsapplication to the details of the particular arrangements shown sincethe invention is capable of other embodiments. Also, the terminologyused herein is for the purpose of description and not of limitation.

The following is a list of the reference numbers used in the drawingsand the detailed specification to identify components:

-   1 upper back reflector-   2 lower back reflector-   3 single-axis opaque side walls-   4 single axis tracking front glazing-   5 single axis redirecting mirrors-   6 back opaque housing-   7 transition tube, rectangular-to-circular-   8 cylindrical reflecting light pipe-   9 redirecting reflecting faceted cone-   10 lower redirecting reflecting ring-   11 redirecting reflecting rings-   12 transition tube housing-   13 fluorescent tube-   14 electric lighting luminaire-   15 electronic dimming ballasts-   16A single axis redirecting mirrors-   16B single axis redirecting mirrors-   17A single axis redirecting mirrors-   17B single axis redirecting mirrors-   18A single axis redirecting mirrors-   18B single axis redirecting mirrors-   19A upper two-axis transparent glazing-   19B lower two-axis transparent glazing-   20 two-axis opaque back housing-   21 two-axis opaque side housings-   22 two-axis adjustable tilt tracking mirror-   23 mirror tracking mechanism-   24 azimuthal tracking mechanism-   25 cylindrical protective sleeve-   26 primary mirror-   27 mirror housing-   28 vertical cylindrical structural-   29 transition tube structural ring-   30 roof flashing-   31 equatorial tracking primary mirror-   32 equatorial curved light pipe-   33 mirror housing-   34 plenum housing-   35 equatorial rotating assembly-   36 equatorial glazing-   37 upper transparent housing-   38 lower transparent housing-   39 upper central bearing-   40 lower central bearing-   41 roof mount-   42 transparent lower support-   43 transparent lower bearing support-   44 spoked lower support-   45 spoked lower bearing mount-   46 lower support-   47 central axis-   48 cylindrical housing w/base-   49 cap-   50 equatorial axis-   51 equatorial bearings and drive-   52 compliant weather seal-   53 transparent thermal barrier-   54 equatorial secondary mirror

The method, system, apparatus and device of the present inventionprovides daylight illumination of a space below where it is placed inthe roof and ceiling immediately above that space, such illuminationbeing relatively constant over the course of a cloudless day. Electriclighting is used to supplement such daylight for periods when the sun isobscured by clouds and at night.

FIG. 1 illustrates the basic configuration of the direct beam solarlighting system. The upper reflector 1, lower reflector 2, and thesidewalls 3 of the solar collector constitute the rotating head or solarcollection subsystem. The drive mechanism 24 is a carousel or “lazySusan” bearing attached to a mounting surface on the roof of a building,where the roof may be either horizontal or sloped. The solar collectorhead is made to rotate so that the entrance aperture always faces thesun's azimuth. The transition tube 7 is a reflective tube having across-section at the top so as to mate with the bottom of the solarcollection subsystem and a circular cross section at its bottom, whereit mates to a cylindrical reflective light pipe 8 that delivers sunlightto a light fixture shown in FIGS. 6 and 11 in the ceiling below. Thelength of the light pipe 8 is adjusted before installation to match theneeds of the particular building in which the invention is installed.Daylight emerges from the luminaire mounted in the ceiling in such amanner that most of it is reflected up to the ceiling and the upperportions of the walls enclosing the illuminated space.

FIG. 2 illustrates the invention schematically. Light from the sunenters the glazed entrance aperture 4, reflects from the upper reflector1 and lower reflector 2 down into the transition tube 7, where it isslightly concentrated and delivered into the reflective cylindricallight pipe 8. Light emerging from the light pipe 8 falls on thereflector 9 or lower redirecting reflector ring 10 which directs lightonto a light-colored ceiling and walls, enabling it to be diffuselyreflected to the space below. The interior surface of the upper backreflector 1, lower back reflector 2, and sides 3 of the sunlightcollector are highly reflective, directing beam sunlight or diffusedskylight reaching the reflective interior surfaces through the glazing 4downward into the light collection and transfer system, transition tube7 and light pipe 8. Sunlight emerging from the bottom of light pipe 8strikes a faceted, segmented or smooth curved (with constant or varyingradius of curvature) conical reflector 9, lower redirecting reflectivering 10, or redirecting reflective rings 11 and is redirected toward theceiling and upper portion of the walls surrounding the illuminatedspace.

The circular reflective ring 10 at the base of the conical reflector 9both shields the light emerging from the bottom of the light pipe 8 fromview by room occupants, minimizing glare, and redirects solar fluxreaching it upward onto the ceiling. The transition tube 7 rotates alongwith the solar collection head above it. The cylindrical light pipe 8may either rotate with the transition tube or remain fixed in place,depending on the configuration desired. A light seal at the intersectionof the fixed and moving circular apertures minimizes light losses intothe attic or plenum space above the ceiling and prevents air flowthrough this crack.

A side view of the solar collection subsystem is illustrated in FIG. 3,which shows the housing 6 of the subsystem, to which the interior upperand lower reflectors 1 and 2 are affixed, and the housing 12 enclosingthe reflective transition tube 7. A representative mechanism 24 forrotating the entire assembly is also illustrated. Any of severalconventional embodiments of a rotating track and wheel or bearingsupport can be used to prevent rainwater, snow, etc. from entering theplenum space between roof and ceiling, while minimizing friction torqueand electrical energy needed to rotate the solar collection subsystem.The design also minimizes losses of solar flux by maintaining thegeometry of the reflective surfaces conducive to reflecting fluxdownward regardless of the relationship between the moving head and thefixed elements of the system.

The solar collector assembly is configured to rotate on this curbed oruncurbed track so that the glazed aperture 4 points toward the sun'sazimuth, within a range of angles of permitted tolerance. With perfecttracking, a normal (perpendicular) vector to the plane of the entranceaperture 4 lies in the vertical plane through the center of the sun.Experimental observation indicates that with this design the toleranceon angular tracking of the sun's azimuth is not strict. The angles ofinclination of top and bottom reflectors 1 and 2 and the glazed entranceaperture 4 are adjusted so that less intense light from the sun at lowsolar altitude angles is captured with good efficiency while thestronger flux from the sun at higher sun angles is partially attenuated,due to shading by the top reflector 1 (reducing the effective aperturearea viewed from the sun), the goal being to provide illumination moreuniformly over the course of the day as the sun rises, reaches its peakheight, and sets.

As shown in FIG. 6, a luminaire, or light fixture, is placed at thebottom of the cylindrical light pipe 8 to redirect light emerging fromthis pipe up onto the ceiling. The luminaire is composed of curved, withconstant or varying radius of curvature, faceted or segmented reflectivecone 9, horizontal circular reflector 10, and ceiling circularreflecting ring 11D as shown in FIG. 6. Light rays emerging from thelight pipe 8 strike various portions of reflective cone 9 and reflectivering 10 and are redirected laterally outward and upward onto the wallsand ceiling of the room. The ceiling and walls are preferably coatedwith a diffusely reflecting material of high reflectivity. Allreflective surfaces within the invention heretofore described arespecularly reflecting, using the highest specular reflectivity materialsuitable for this purpose.

In the event that these specularly reflecting surfaces are imperfect intheir shape or figure, producing nonuniform illumination of the ceilingand walls of the room, one or more of the reflecting surfaces may begiven a semi-diffuse optical reflectivity such that the reflected fluxis as strong as before, but is spread slightly from the speculardirection, as a means to soften the occasional bright spots that may beevident in the reflected illumination.

For maximum energy conservation, the electric lights in the room aredimmed automatically whenever daylight from the invention is sufficientto illuminate the room. This dimming is adjusted to the minimum levelnecessary to obtain the desired average task plane illuminance over thespace, thereby using the least amount of electric lighting energypracticable. The dimming may be accomplished electronically through theuse of dimming ballasts or by switching off various banks of electriclights incrementally to maintain illumination levels desired. Whendaylight is sufficient, the electric lighting system is switched offcompletely. The electric lighting system may be incorporated into thecurrent device or a separate unit.

FIG. 7 indicates one possible way that an electric luminaire can beincluded in the design of the current invention. Flouorescent or otherlamps 13 are placed around the perimeter and below the lower reflectingdisk 19 and are surrounded by approximately parabolic reflectors 14.These reflectors direct light from the lamps radially outward to thewalls and ceiling of the room. Fluorescent ballasts 15, if used, may beincluded in the housing of the invention, as shown in FIG. 7.

Additional components, or modifications, may be added to the basicdesign previously described, for the purposes of improving performanceor for customizing the invention to meet specific applicationrequirements. FIGS. 4 and 5 illustrate an alternative configuration ofthe invention. FIG. 4 shows a 3-dimensional perspective view of thesolar collection device encapsulated within a fixed, non-rotatingtransparent housing 37 and a lower portion of the fixed housing 38 or46, the sides of which may be transparent 38 or not 46, and the opticalcollection and delivery subsystems including the upper and lowerreflectors 1 and 2 and the transition tube 7. The bottom of rotatingmechanism connects to the vertical axle 47 with either a set of spokes44 or a transparent disk 42 (FIG. 5) and is supported by eithertransparent disk 43 or spoked wheel 45. The transparent lower bearingsupport 43 or the spoked lower bearing mount 45 shown in FIG. 5 is fixedand non-rotating and spoked lower support 44 or transparent lowersupport 42 rotates with the optical collection subsystem above it. Uppercentral bearing 39 and lower central bearing 40 are the bearings,bushings or other means of reducing friction supporting the rotatingoptical collection subsystem and driving its rotating motion.

The upper reflector 1, lower reflector 2, the sidewalls 3, andtransition tube 7 of the solar collector constitute the rotatingelements of the solar collection subsystem and are contained within afixed transparent enclosure 37. The transparent enclosure 37 and thelower support 46 are held in position by the roof-mounted structure 41,where the roof may be either horizontal or sloped. The rotating elementsare made to rotate so that the entrance aperture, a rectangular openingin the position occupied by glazing 4 in the previous embodiment butwithout the glazing in this alternative configuration faces the sun inazimuth.

The transition tube 7 is a reflective tube having a non-circularcross-section at the top where it mates to the bottom of the solarcollection subsystem and a circular cross section at its bottom, whereit aligns with a cylindrical reflective light pipe 8, if required, thatdelivers sunlight to a reflective cone 9 and lower redirectingreflective ring 10 in the ceiling below. The base of the transition tubeis connected to the lower central axis 47 via either a sheet oftransparent material 42 or a plurality of narrow spokes 44.

FIG. 5 shows a side view of the solar collection subsystem including thetransparent enclosure 37 of the subsystem which supports the uppercentral bearing 39 to which the interior rotating reflectors 1 and 2 andreflective transition tube 7 are affixed via the central axis 47. Thelower central support bearing 40 is supported by a transparent mountingplate 43 or a spoked wheel 45, to provide structural support with amaximum of light throughput. The upper and lower back reflectors 1 and 2rest upon the transition tube 7 which in turn is mounted to atransparent lower bearing mount 42 or the spoked wheel 45, as required.

A perspective view of the solar collection system is illustrated in FIG.4, which shows the use of a plurality of spokes 44 to replace thetransparent mounting plate 42 and another plurality of spokes 45 inplace of the transparent lower bearing mount 43.

FIG. 7 shows an alternative configuration that incorporates the room'selectric lighting system with the solar lighting system of the presentinvention. For example, a second ring reflector 14 may be added. Thissecond reflector ring 14 is planar on its outer rim, but curves upwardin an approximately parabolic shape, providing redirecting reflectors toreflect light from the fluorescent tubes 13 of electric light fixture 14outward onto the upper portions of the walls of the room and onto theceiling. Electronic ballasts 15 are used to dim the light from thefluorescent lamps 13 when lighting from the solar lighting system isadequate, shutting off the electric light fixture 14 when light providedby the solar lighting system is sufficient to illuminate the room to thedesignated minimum level. Alternatively, one or more lamps areselectively turned on and off so that electric light supplementingavailable solar lighting can be varied step-wise from off through anumber of steps to all lamps being full on.

In order to ensure that for all sun angles, rays entering the solarcollection assembly from the sun are directed downward onto all portionsof the reflective cone 9 and reflective ring 10, reflective vanes 5 maybe added to the solar collection assembly to redirect sunlight downwardthrough the transition tube and light pipe more evenly over theretroreflector, reflective cone 9 and reflective ring 10. Thepositioning of these reflective vanes 5 is shown in FIG. 8. The anglesof tilt of these reflective vanes are varied slightly from the bottomvane to the top vane and the width may be varied up to the diameter ofthe light pipe 8 below. Alternatively, the reflective vanes 5 may extendthe full width of the solar collection head, being attached to the sidewalls 3 of the assembly. FIG. 9 is a side-view of the solar collectionhead, illustrating the placement of these beam-homogenizing reflectivevanes 5A through 5D in more detail. The tilt angles shown areapproximate.

FIGS. 10 and 11 illustrate another alternate configuration for reducingglare in the room due to light emerging from the bottom of light pipe 8,additional specular or combined specularly and diffusely reflectingplanar, faceted, or curved with constant or varying radius of curvature,rings 11A through 11C may be placed between the lower reflector 10 andthe ceiling reflector 11D, as shown. If more light is desired in thecenter of the illuminated space than around the perimeter of it, morediffuseness can be used in the reflecting properties of these rings,keeping light leaving the light pipe from propagating as far from theluminaire as would be the case with highly specular rings. Asemi-diffuse reflecting property can also be helpful to soften theillumination of the room, reducing and spreading bright spots.

In addition, an optional clear or slightly diffusely transmittingtransparent cylinder, or sleeve 25 may be placed as shown around theoutside of this stack of rings, extending from the bottom one 10 to thetop one 11D on the ceiling, as shown in FIG. 12, to prevent theaccumulation of dust or objects from being tossed into the luminairefrom the room below. As shown in FIG. 12, the transparent ring 25 slidesup over the edges of the lower reflective ring 10, and intermediatereflecting rings 11, if installed, as shown. Such a transparent cylinder25 can also serve the purpose of softening or dispersing the daylightemerging from the luminaire toward the walls and ceiling of the room.

FIGS. 13 and 14 illustrate another means of homogenizing the sun's raysfollowing reflection from upper and lower reflectors 1 and 2,respectively. This configuration consists of crossed reflective vanes16A and 16B placed in the transition tube 7 or further down the lightpipe 8. Additional vanes may also be added to this configuration toalter or improve performance. The length of the reflective vanes 16A and16B can vary up to the length of the transition tube 7 or light pipe 8,whichever they are mounted in.

Still another method for homogenizing the beam is shown in FIG. 15.Concentric cylindrical, elliptical, or otherwise oval or taperedreflective surfaces 17 may be placed inside of the transition tube 7 orlight pipe 8, for reflecting angled rays reaching them more uniformlyover the luminaire surfaces below. A rectangular variation on the curvedbeam homogenizer shown in FIG. 15 is illustrated in FIG. 16. Openrectangular boxes 18 made of highly reflective material are suspendedwithin the transition tube 7, or light pipe 8. In all configurations thevanes, cylinders, elliptical, square, or rectangular devices used tohomogenize the light beam may be of constant or varying cross sectionand may be of flat, faceted, curved (of constant or varying radius ofcurvature) surfaces.

In the configuration shown in FIG. 17, the planar upper and lowerreflectors 1 and 2 shown and previously described, are replaced by afaceted or curved reflector 26 on the inside of a faceted or curvedhousing 27 that better conforms to the shape of the reflectors 26.

Several companies manufacture and market tubular daylighting devices inthe United States and abroad. They include Solatube, ODL, Natural Light,and Velux. Most of them use a clear dome at the top of a verticalcylindrical reflective light pipe that projects above the roof plane,extends downward through the roof and attic or plenum space to theceiling of the room below. A diffusing glazing, planar or domed, isaffixed to the bottom of the light pipe at the ceiling level, therebyspreading the light received by it over the room area beneath thediffuser. Some of these products incorporate reflectors or refractingelements in the design of the top dome (or placed just below it) toimprove early morning or late afternoon performance, but with verymodest, if any, improvement.

In this configuration, the top dome and associated optical elements of acommercially available tubular skylight are removed, leaving thereflective cylindrical light pipe protruding up from the roof. A supportsleeve 28 is placed over the cylindrical light pipe and mounted firmlyto the roof of the building. A smaller version of the solar collectionand tracking head, including upper and lower back reflectors 1 and 2,opaque side walls 3, and/or transition tube 7 is placed on top of sleeve28, using mounting ring 29 attached firmly to the transition tubehousing 12. Sleeve 28 is mounted firmly to the roof surface and at itsbottom and supports the rotating head, upper and lower back reflectors 1and 2, opaque side walls 3, front glazing 4, back opaque housing 6,transition tube 7, and transition tube housing 12, as shown in FIGS. 18and 19. Ring 29 is firmly affixed to the bottom of the transition tubehousing 12 and contains the mechanism 24 that rotates (in azimuth only)the solar collector head above, to track the sun's movement. Therotating mechanism 24 in FIG. 19 is similar in function to mechanism 24shown in FIG. 3.

Transition tube housing 12 surrounding the transition tube 7 may bestrengthened in this version of the invention so that it supports itselfand the solar collection assembly component's upper and lower reflectors1 and 2, respectively, side walls 3, glazed entrance aperture 4, and theback housing 6 described above, with sufficient strength to withstandexpected wind loading forces. A motor for driving the rotation ispowered by the electric grid or a small photovoltaic (PV) cell array andassociated elements of a PV-powered system, such as large capacitor,batteries, and associated charging circuits, and voltage regulators, orother source of electricity.

FIG. 19 provides a side view schematic illustration of this fifthembodiment of the invention. The base of the sleeve 28 fitting over atubular skylight reflective cylinder is sealed to the roof through theuse of roof flashing 30, using any of a variety of flashing techniquescommonly known to roofing technicians. If needed and used, sleeve 28 ismade of material strong enough to support the solar collection head andits rotating mechanism as well as to hold it tightly to the building inthe event of high winds. This modification enhances the performance ofthe tubular skylight by increasing illumination levels at all sunangles, but preferentially more at low sun angles, making the lightlevel in the space below more uniform throughout the day. With itslarger solar collection aperture 4, tracking ability, and other designfeatures, the added tracking head delivers more light to the light pipe8 and improves the tubular skylight performance all day long.

Alternatively, a support sleeve 28 is placed over the cylindrical lightpipe and mounted firmly to the roof of the building as shown in FIGS. 20and 21. A smaller version of the solar collection and tracking head,including the upper and lower back reflectors 1 and 2, opaque side walls3, and/or transition tube 7 which are contained in a transparentenclosure 37 and non rotating supporting ring 43, is placed on top ofsleeve 28 and sealed from water and airflow via compliant seal 52.Sleeve 28 is mounted firmly to the roof surface and at its bottom andsupports the rotating head, items upper and lower back reflectors 1 and2, opaque side walls 3, transition tube 7, upper central bearing 39,transparent or spoked lower support 42 or 44, central axis 47 andtransparent or spoked mounting supports 43 or 45, and lower centralbearing 40. Within the transparent enclosure 37 the mechanism comprisingof the reflecting elements upper and lower back reflectors 1 and 2,opaque side walls 3, and transition tube 7 as well as support element 42or 44 rotate (in azimuth only) around shaft 47 on bearings 39 and 40.The solar collector head thus rotates, to track the sun's movement. Therotating mechanism shown in FIG. 20 is similar in function to themechanism shown in FIG. 4. A motor for driving the rotation is affixedto axle 47 near either bearing 39 or 40.

FIG. 21 provides a side view schematic illustration of this sixthembodiment of the invention. The base of the sleeve 28 fitting over atubular skylight reflective cylinder is sealed to the roof through theuse of roof flashing 30, using any of a variety of flashing techniquesknown to roofing technicians. If needed and used, sleeve 28 is made ofmaterial strong enough to support the solar collection head as well asto hold it tightly to the building in the event of high winds. Thismodification allows for very simple upgrades from a simpleupwards-facing dome which is standard with tubular skylights to anactive tracking system. All moving parts are protected from damageduring installation or following installation from the effects ofweather. By having all of the parts pre-assembled within the transparentdome, both the number of steps and the precision required for roof-topmounting are greatly reduced.

Instead of using diffusers at the bottom of the light pipe,retroreflectors 9 as shown in FIG. 2 for example, may be used to achievebetter distribution of the resulting natural light, avoid glare, andprovide for integrated electric lighting in an effective fashion.

The solar collector head can be made to accomplish two-axis tracking ofthe sun, improving performance over the full range of solar altitudeangles at increased manufacturing cost, while keeping the same basicconcept of the present invention. This alternative is illustrated inFIG. 22. The transition tube 7, the light pipe 8, and the reflectivecone 9, lower reflective ring 10 and reflection rings 11 are retained.However, the sun-facing glazing 4 of the previous design is replaced byupper and lower rectangular glazings 19A and 19B and the back of thecollection box 20 becomes a single opaque rectangular piece that doesnot have to be reflective. A single rectangular mirror 22 is placed inthe box and hinged at the bottom, so that it may track the sun inaltitude. The azimuth tracking assembly remains in place and in use asbefore, but now the fixed back reflectors 1 and 2 are replaced by themovable single reflector 22 shown in FIG. 22.

FIG. 23 illustrates schematically the operation of the two-axis trackingadjustable tilt tracking minor 22. An actuator assembly 23 moves themirror back and forth on its hinge at the bottom to half the angle ofthe solar altitude, so that the reflected rays from the sun are beamedmore nearly vertically downward into the transition tube andconcentrator 7 below, and thence into the light pipe 8, for all solaraltitude angles. Any of a variety of actuator methodologies may beemployed to the adjustable tracking mirror 22. Either one or both of thetwo planar glazings 19A and 19B may be replaced in an alternativeversion of this design with a curved single glazing.

As previously described, various beam homogenizing reflective structuressimilar to those illustrated in FIGS. 13 to 16 may be added to thetransition tube 7 to more evenly illuminate the solar luminaire below.

The solar lighting system of the present invention may be modified toincorporate an equatorial tracking design wherein the primary mirrorrotates about an axis parallel to the axis of the Earth's rotation.Thus, the minor's rotational axis is inclined at an angle up from thehorizontal equal to the site latitude. To accommodate a wide range ofsite latitudes, two approaches are envisioned in the design. The firstis to manufacture several different models designed to work best atsites exactly on latitudes between approximately 0 degrees andapproximately 90 degrees, preferably 0, 15, 30, 45, 60, and possibly 75degrees north or south of the equator. Performance at sites betweenthese latitudes will be slightly compromised, but not enough to degradeperformance significantly, since in no case will the tilt of theequatorial axis be off by more than 7.5 degrees. The second solution tothis problem will be to include a gimbled or adjustable tilt angle inthe design of the product, so that it can be adjusted in the factory orin the field to the latitude of the installation.

Another configuration of the invention is an equatorial tracker,illustrated schematically in FIG. 24. An elliptical minor 31 rotatesabout axle 50 which is supported by two bearings 51 and is completelyenclosed in the cylindrical transparent housing 48 and cap 49.Cylindrical transparent housing 48 holds transparent lower bearingsupport 43 or spoked lower bearing support 45 onto which one of thebearings 51 is mounted. The other bearing 51 is mounted to cap 49. Theaxis of axle 50 is aligned so that it is parallel with the axis of theearth. Practically, this means that it is tilted down from vertical inthe direction of true north by the amount of 90 degrees minus thelatitude of the location of the unit.

The cylindrical transparent housing is affixed to curved light pipe 32and provides a seal from the elements of weather. Mirror 31 is rotatedabout axle 50 to track the movement of the sun and thus direct sunlightinto curved light pipe 32. At an equinox, the rays from the sun areperpendicular to the Earth's axis and thus perpendicular to axle 50 atall times causing the reflected rays from the primary mirror 31 to beparallel to axle 50. The rotation of mirror 31 on axle 49 ensures thatthe reflected rays are parallel to axle 50 all day long on theequinoxes. The reflected equinoctial rays enter a curved light pipe 32where they are reflected downward to the same retro reflectors includingthe redirecting reflecting faceted ring 9, the lower redirectingreflecting ring 10, redirecting reflecting rings 11A-D, and theadjusting tilt tracking mirror 22, as shown in FIG. 4 for example.Tracking primary mirror 31 is elliptical in shape, so that raysreflected from it during the equinoxes fully fill the circular apertureof the transparent cylindrical housing 48 and of the circularcross-section bent light pipe 32. A transition tube 7 is not requiredwith this configuration. Light pipe 32 becomes cylindrical once itenters the plenum space between roof and ceiling, enclosed by housing34.

At other times of the year rays from the sun, shown as dashed and dottedlines in FIG. 24 strike the primary mirror 31 at other than 45 degreesand are reflected into the curved light pipe 32 at varying angles, wherethey are still channeled down to the reflective cone 9, and othercomponents of the ceiling luminaire described previously. With thisdesign the transition tube 7 of previous embodiments is no longerneeded.

A dual axis tracking version of the equatorial tracking design is shownin FIG. 25. In this configuration, the primary mirror 31 rotates aboutan axle parallel to the Earth's axis as before, but also rotates aboutan axis orthogonal to the axle to accommodate seasonal variations in thesun's position, thereby directing reflected sunbeams directly onto thefixed secondary mirror 54 and thence vertically downward to the solarluminaire at and below the ceiling level. Bearings and motors 51 drivethe two motions of mirror 31, which is suspended on the axle 50. Thecylindrical transparent cover 48 and end cap 49 are retained and thewhole solar collecting head is held in place by mounting structure 33.

Another configuration of the present invention is shown in FIG. 26wherein the rotating mirror 31 of the equatorial designs is held insidea rotating housing 33 with a planar entrance window 36. The whole headrotates about an axis of rotation parallel to the Earth's axis ofrotation. The reflected rays from the sun enter a curved cylindricallight pipe and are thereby directed downward onto the solar luminaire atthe ceiling level below. The rotating assembly 35 is similar to thatillustrated for the horizontal rotating ring in FIG. 3.

An open-loop means for manipulating the solar collection head with itstransition tube in azimuth and the variation that includes a mirror fortracking in elevation is incorporated. The electronics involved arebased on a microprocessor system that does not rely on external sourceof information, other than latitude, longitude, and time, to accuratelypoint the system to the sunlight from any point on the earth's surface.The microprocessor is programmed with appropriate public domainequations of the movement of the sun so that the user only inputslatitude and longitude at time of the installation of the invention. Inaddition, the current local time is entered, and re-entered as neededperiodically. The internal clock is very accurate so only yearlyresetting is required. An alternative design includes a WWV receiver toautomatically reset the time periodically.

The system employs a sensor to communicate to the control mechanism whenthe head is in a particular orientation for calibration purposes andthen it operates automatically. In particular, the system moves the headwhen the error is greater than some specified tolerance from the azimuthof the sun. The system is adjusted so that looser or tighter control ofpointing direction can be enabled. This permits the control system to beused with other solar devices where higher accuracy is necessary orlower accuracy is permitted and power consumption needs to be reduced.

The control system is accurate, durable, easy to set up, occupies asmall package, uses very little electrical energy, and may be powered byeither a small dc power supply or by Photo Voltaic cells charging eithera large capacitor or battery. It includes controls to enablesemi-automatic and manual adjustment of the systems steered with respectto the sun to temporarily diminish the amount of sunlight distributed tointerior spaces to allow for audio visual presentations and for otherreasons as desired.

In summary, the present invention provides a new method, system,apparatus and device to track the sun in azimuth and accommodate bypassive or active optical means changes in solar altitude (elevation)angle over the course of a day, transferring a significant fraction ofthe direct beam sunlight incident on the aperture uniformly across theceiling of a space below the device and to maintain this ceilingindirect illumination of the space reasonably constant over the courseof most of the daylight hours, whenever the sun is not obscured byclouds. It thus provides well distributed light to surfaces below thatis largely free of glare. It also provides modest solar heating to anamount that may be varied by adjusting the solar heat gain coefficientof the various clear and reflective optical surfaces incorporated intoeach configuration.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

1. A method for collecting and distributing sunlight into an interiorspace of a building comprising the steps of: tracking a position of thesun with a rotatable solar collector head to receive sunlight andreflect the received sunlight downward, the rotatable solar collectorhead including a housing, an upper and lower back reflector and sidewallreflectors on an interior surface of the housing to capture and deflectthe received sunlight downward, and an entrance aperture in a front sideof the housing approximately opposite the upper and lower backreflectors and facing horizontally to allow sunlight to enter therotatable solar collector head, wherein the rotatable solar collectorhead accommodates vertical solar altitude variations to increasereceived sunlight throughput at low sun angles and attenuate thereceived sunlight throughput at high angles to provide illuminationthroughout daylight hours; rotating the rotatable solar collector headwith a drive mechanism about a vertical axis to track the sun's movementin azimuth; receiving and concentrating the reflected sunlight with atransition tube having a reflective interior surface with a first end ofthe transition tube connected with the rotatable solar collector head;further directing the reflected sunlight through a plenum space into theinterior space below with a reflective light pipe connected to a secondend of the transition tube; and disbursing the reflected sunlight onto aceiling and walls of the interior space below with a retroreflector atthe end of the reflective light pipe.
 2. The method of claim 1 whereinthe rotating step includes the step of: using a rotating track and wheelassembly to rotate the rotatable solar collector head.
 3. The method ofclaim 1 wherein the rotating step includes the steps of: supporting therotatable solar collector head on a roof of a building with a bearing;and supporting the bearing between the solar collector head and thelight pipe with a support member to minimize solar light loss.
 4. Themethod of claim 3 further comprising the step of: selecting the supportmember from a group consisting of a transparent surface or a pluralityof narrow spokes.
 5. The method of claim 1, wherein the disbursing stepincludes the steps of: shielding the sunlight emerging from the lightpipe and directing light onto the ceilings and walls to be diffuselyreflected to the space below using a redirecting reflecting cone with ahorizontal circular reflector at a base of the reflecting cone of theretroflector.
 6. The method of claim 5, further comprising the step of:further directing light onto the ceilings and walls to be diffuselyreflected to the space below with a ceiling reflecting ring.
 7. Themethod of claim 6, further comprising the step of: providing a stack ofhorizontal reflector rings placed around the cone reflector between theceiling reflecting ring and the horizontal circular reflector forreducing glare from the light fixture to send more light to the ceiling,wherein a diffuseness of the reflecting surfaces is varied according toa desired illumination of the room.
 8. The method of claim 7 furthercomprising the step of: providing a transmitting transparent sleevearound the outside of the stack of horizontal reflector rings toeliminate dust or objects from accumulating on the stack of horizontalreflector rings and to further vary the sunlight emerging from theretroflector.
 9. The method of claim 6, wherein the disbursing stepfurther comprises the step of: redistributing rays reflected downwardinto the light pipe with a set of reflective surfaces in the transitiontube.
 10. The method of claim 6, wherein the disbursing step furthercomprises the step of: redistributing rays reflected downward with a setof concentric reflective surfaces in the light pipe.
 11. The method ofclaim 10 further comprising the step of: selecting the set of concentricreflective surfaces from the group consisting of cylindrical,elliptical, oval, square, rectangular or tapered reflective surfaces.12. The method of claim 1, wherein the tracking step further comprisesthe step of: redistributing rays reflected downward into the transitiontube and light pipe more evenly over the retroflector with a set ofrectangular reflecting vanes.
 13. The method of claim 1, wherein thetracking step further comprises the step of: redistributing raysreflected downward into the transition tube or the light pipe with acrossed reflective vane.
 14. The method of claim 1, further comprisingthe step of: housing the rotatable solar collector head, drive mechanismand the transition tube with a transparent enclosure mounted on the roofto prevent exposure to external weather.
 15. The method of claim 1wherein the tracking step further comprises the step of: providing acurved housing having a curved side and a curved back side with anentrance aperture approximately opposite the curved back side, a curvedback reflector on the inside curved back of the curved housing, andcurved side reflectors on the curved side of the housing.
 16. The methodof claim 1 wherein the tracking step further comprises the step of:providing a faceted housing having a faceted side and a faceted backside with an entrance aperture approximately opposite the faceted backside, a faceted back reflector on the inside faceted back of the facetedhousing, and faceted side reflectors on the faceted side of the housing.17. The method of claim 1 wherein the tracking step further comprisesthe step of: providing a hinged and rotating reflective surface withinthe housing to reflect sunlight downward into the transition tube,wherein the method provides two-axis tracking.
 18. The method of claim 1wherein the tracking step further comprises the step of: providing thehousing with a collection box having an opaque back panel, a transparentpanel and side panels, a movable reflector hingedly connected to thecollection box, and an actuator assembly for moving the reflector totrack the sun in altitude and the sunlight is beamed vertically downwardinto the transition tube.
 19. The method of claim 18 further comprisingthe step of: providing the transparent panel with a transparent upperpanel and a transparent lower panel.
 20. The method of claim 1 furthercomprising the step of: providing a second axis for tracking of the sunin elevation with a tiltable mirror pivotedly connected to the solarcollector head that is rotated about a horizontal axis.
 21. The methodof claim 1 wherein the receiving and concentrating step comprises thestep of: increasing the illuminance emerging from the transition tubewith an entrance aperture in the first end that mates to the bottom ofthe head and an exit aperture in the second end that is circular,wherein the circular exit aperture is smaller than the entrance apertureto increase the illuminance emerging from the circular exit aperture.22. The method of claim 1 wherein the rotating step comprises the stepof: providing a controller for automatically adjusting alignment of thehousing with respect to location of the sun through azimuthal trackingabout a vertical axis.
 23. The method of claim 1 wherein the disbursingstep comprises the step of: dispersing light around said room with alight diffuser at the bottom of said light tube, the diffuser includinga segmented, nominally conical shape of specularly reflective material;uniformly distributing sunlight throughout the room with surroundingplanar, horizontal, parallel rings spaced vertically; and surroundinglayered rings with a cylindrical transparent cover to physically protectand be capable to spread the light emerging from the light tube.
 24. Themethod of claim 1 further comprising the step of: coupling an electricallight source with the housing to complement the sunlight reflected intothe interior area when the sunlight falls below a desired illuminationlevel.
 25. The method of claim 24 further comprising the step of:automatically controlling an amount of illumination from the electricallight source to maintain the desired illumination level with acontroller.
 26. The method of claim 1 further comprising the step of:tracking the sunlight with a circular-aperture tracking system having aglazed aperture in the solar collector head that faces an equinoctialsun directly and a rotatable mirror with an axis of rotation that isparallel with the Earth's rotational axis, wherein the rotatable mirrorreflects equinoctial rays perpendicularly into the light pipe, the lightpipe having a bottom portion of which is a right circular cylinder whoseaxis is vertical and passes through the roof to the ceiling of theinterior space.
 27. The method of claim 26 wherein the receiving andconcentrating step comprises the step of: connecting an equatorialcurved light pipe with a cylindrical transparent housing affixed to thecurved light pipe from an external environment to the solar collectorhead as the transition tube.
 28. The method of claim 26 wherein thetracking step further comprises the step of: rotating a primary mirrorabout a first axis parallel to the Earth's axis and about a second axisorthogonal to the first axis to accommodate seasonal variations in theposition of the sun; driving the two motions of the primary mirror witha drive system; and receiving the sunlight reflected from the primarymirror and reflecting it to a fixed secondary mirror to theretroflector.
 29. The method of claim 26, wherein the tracking stepfurther comprises the step of: rotating the head about an axis parallelto the Earth's axis of rotation with a rotatable housing with a planarentrance window.
 30. The method of claim 1 further comprising the stepsof: covering an existing tubular skylight light pipe after a top domeand associated optical elements are removed with a support sleeveconnected with the roof of the building, wherein the head and thetransition tube are placed on top of the support sleeve; and firmlyaffixing a ring to the second end of the transition tube, the ringcontaining the drive mechanism for rotating the head.